Induction hardening apparatus, induction hardening method, induction heating coil, heat treatment apparatus, and heat treatment method

ABSTRACT

According to an embodiment, an induction heating coil includes a heating conductor portion which is formed of a conductor member and has a zigzag shape in which a bent portion opened to one side in a first direction and a bent portion opened to the other side in the first direction are alternately continuously arranged in opposite directions along a second direction crossing the first direction.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of application Ser. No. 13/360,274,filed Jan. 27, 2012, which is a continuation of PCT/JP2010/062847, filedJul. 29, 2010, which claims priority to Japanese Patent Application Nos.2009-178256, filed Jul. 30, 2009; 2010-121901, filed May 27, 2010;2010-150411, filed Jun. 30, 2010; and 2010-157556, filed Jul. 12, 2010,the entire disclosures of which are hereby incorporated by referenceherein.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates to an induction hardening apparatus, aninduction hardening method, an induction heating coil, a heat treatmentapparatus, and a heat treatment method, and more particularly to atechnology for improving heat treatment efficiency and performing auniform treatment.

2. Description of the Related Art

In an induction hardening method for performing a heat treatment such ashigh-frequency hardening with respect to a metal member, there has beenknown a heat treatment apparatus adopting a single shot heating processfor using an induction heating coil facing an entire treatment targetregion to collectively perform a treatment (e.g., Jpn. Pat. Appln. KOKAIPublication No. 2005-120415, Jpn. Pat. Appln. KOKAI Publication No.2002-174251, or Jpn. Pat. Appln. KOKAI Publication No. 2004-44802). Insuch a heat treatment apparatus adopting the single shot heatingprocess, the induction heating coil is formed into a shape associatedwith the entire treatment target region. For example, an annularinduction heating coil is arranged to face a treatment target portionwhen the treatment target portion has a circular shape, and a tabularinduction heating coil is arranged to face a treatment target portionwhen the treatment target portion has a planar shape. Since such aheating apparatus adopting the single shot heating process uses theinduction heating coil to cope with various shapes and sizes of atreatment object and a treatment target portion, a large inductionheating coil is required and high-output power is needed when thetreatment object and the treatment target portion are large.

On the other hand, there has been known a scanning heat treatmentapparatus for sequentially performing a heat treatment and a coolingtreatment while relatively moving an induction heating coil, which facesa part of a treatment target portion alone, with respect to thetreatment target portion (e.g., Jpn. Pat. Appln. KOKAI Publication No.2005-89803, or Jpn. Pat. Appln. KOKAI Publication No. Sho 60-116724). Insuch a scanning heat treatment apparatus, the induction heating coil isformed into a shape associated with a part of the treatment targetportion.

The technology of the induction heating has the following problems. Thatis, in the induction hardening apparatus adopting the single shotheating process, since the induction heating coil associated with a sizeor a shape of the treatment target portion must be used, for example,when the treatment target portion has a complicated shape, a shape orcondition setting of the induction heating coil becomes complicated, andrealizing the apparatus is impossible. Furthermore, when the treatmenttarget portion is large, and a big induction heating coil is required,this results in a problem that high-output power is required. Moreover,when the treatment object is deformed due to, e.g., thermal expansion atthe time of induction heating, maintaining an appropriate dimensionbetween the induction heating coil and the treatment object isdifficult. Therefore, the induction heating coil must be set to have alarger size in advance, and hence a problem of poor heating efficiencyoccurs.

On the other hand, in the scanning heat treatment method, when theinduction heating coil is formed into a shape associated with a part ofthe treatment target portion, a treatment area per unit time is small, atreatment time is increased, and treatment efficiency is deteriorated.Additionally, in the case of moving the induction heating coil whilecontinuously performing the heat treatment and the cooling treatment,for example, when an annular treatment target portion is to be treated,there occurs a problem of generation of a soft zone, which means thenecessary hardness cannot be obtained at a boundary between a startportion and an end portion of the treatment.

Therefore, it is an object of the present invention to provide atechnology that can readily realize a heat treatment for a desiredregion to be heated without requiring high power, a technology thatenables a uniform treatment, and a technology that enables improvingheat treatment efficiency when performing induction heating on even alarge treatment object.

BRIEF SUMMARY OF THE INVENTION

According to one embodiment, an induction hardening apparatus comprisesheating coils comprising heating conductor portions that inductivelyheat different parts of the treatment target portion in an axialdirection crossing the circumferential direction, and at least one ofthe heating coils has a heating conductor portion having a zigzag shapein which a bent portion that is opened to one side in the axialdirection and a bent portion opened to the other side in the axialdirection are alternately continuously arranged in opposed directionsalong the circumferential direction wherein a treatment object and aheating coil are relatively moved along a circumferential direction of atreatment target portion of the treatment object based on rotationalmovement or at least one of the treatment object and the heating coil.

According to another embodiment, an induction hardening method comprisesa moving and heating step of arranging heating coils, which have heatingconductor portions that inductively heat different parts of a treatmenttarget portion of a treatment object in an axial direction crossing acircumferential direction, to face at least a part of the treatmenttarget portion and relatively moving the treatment target portion andthe heating coils along the circumferential direction of the treatmenttarget portion while performing a heat treatment on the treatment targetportion using the heating coils, wherein respective regions of thetreatment target portion heated by the heating conductor portions of theheating coils form one continuous heating region, and

at least one of the heating coils has a zigzag shape in which a bentportion opened to one side in the axial direction and a bent portionopened to the other side in the axial direction are alternatelycontinuously arranged in opposite directions along the circumferentialdirection.

According to another embodiment, an induction heating coil comprises aheating conductor portion which faces at least a part of a treatmenttarget portion and performs a heat treatment for the treatment targetportion while relatively rotationally moving with respect to thetreatment target portion, wherein the heating conductor portioncomprises a conductor portion that extends to cross the circumferentialdirection of the rotation and has a configuration such that a length inthe circumferential direction of a part apart from the center of therotational movement is longer than a length in the circumferentialdirection of a part close to the center.

According to another embodiment, an induction heating coil comprises aheating conductor portion which is formed of a conductor member and hasa zigzag shape in which a bent portion opened to one side in a firstdirection and a bent portion opened to the other side in the firstdirection are alternately continuously arranged in opposite directionsalong a second direction crossing the first direction.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

FIG. 1 is a cross-sectional view taken along a line F2-F2 in FIG. 2showing an induction hardening apparatus according to a first embodimentof the present invention from a direction of an arrow in FIG. 2;

FIG. 2 is a plan view showing the induction hardening apparatusaccording to the first embodiment;

FIG. 3 is a plan view showing a first induction hardening apparatusaccording to the first embodiment;

FIG. 4 is a front view showing a first heating coil according to thefirst embodiment;

FIG. 5 is a plan view showing a second induction hardening apparatusaccording to the first embodiment;

FIG. 6 is a front view showing a second heating coil according to thefirst embodiment;

FIG. 7 is an explanatory view showing a cross-sectional configuration ofthe heating coil according to the first embodiment;

FIG. 8 is an explanatory view of first and second heating regionsaccording to the first embodiment;

FIG. 9 is an explanatory view of a third heating region according to thefirst embodiment;

FIG. 10 is an explanatory view showing a configuration of a heatingconductor portion in an induction hardening apparatus according to asecond embodiment of the present invention;

FIG. 11 is an explanatory view showing a configuration of the heatingconductor portion in the induction hardening apparatus;

FIG. 12 is an explanatory view showing an induction hardening apparatusaccording to a third embodiment of the present invention;

FIG. 13 is en explanatory view showing a primary part of an inductionhardening apparatus according to a fourth embodiment of the presentinvention;

FIG. 14 is an explanatory view showing an induction hardening apparatusaccording to a fifth embodiment of the present invention;

FIG. 15 is an explanatory view of a heating coil incorporated in aninduction hardening apparatus according to a sixth embodiment of thepresent invention;

FIG. 16 is a front view of a heating coil incorporated in an inductionhardening apparatus according to a seventh embodiment of the presentinvention;

FIG. 17 is an explanatory view showing an induction hardening apparatusaccording to an eighth embodiment of the present invention;

FIG. 18 is an explanatory view showing an induction hardening apparatusaccording to a ninth embodiment of the present invention;

FIG. 19 is an explanatory view showing an induction hardening apparatusaccording to a 10th embodiment of the present invention;

FIG. 20 is an explanatory view showing an induction hardening apparatusaccording to an 11th embodiment of the present invention;

FIG. 21 is an explanatory view showing an induction hardening apparatusaccording to a 12th embodiment of the present invention;

FIG. 22 is an explanatory view showing an induction hardening apparatusaccording to a 13th embodiment of the present invention;

FIG. 23 is a plan view showing an induction heating apparatus accordingto the 13th embodiment;

FIG. 24 is a perspective view showing a heating coil according to the13th embodiment;

FIG. 25 is an explanatory view of a conductor portion of the heatingcoil according to the 13th embodiment;

FIG. 26 is an explanatory view showing a cross sectional configurationof the heating coil according to the 13th embodiment;

FIG. 27 is a perspective view showing a heating coil in an inductionheating apparatus according to a 14th embodiment of the presentinvention;

FIG. 28 is a plan view showing the heating coil;

FIG. 29 is a side view showing the heating coil;

FIG. 30 is an explanatory view showing a configuration of a conductorportion of the heating coil;

FIG. 31 is an explanatory view showing an induction hardening apparatusaccording to a 15th embodiment of the present invention;

FIG. 32 is an explanatory view showing a configuration of a conductorportion according to a 16th embodiment of the present invention;

FIG. 33 is an explanatory view showing a configuration of a conductorportion according to a 17th embodiment of the present invention;

FIG. 34 is an explanatory view showing a heat treatment apparatusaccording to an 18th embodiment of the present invention;

FIG. 35 is a plan view showing the heat treatment apparatus according tothe 18th embodiment;

FIG. 36 is a side view showing the heat treatment apparatus according tothe 18th embodiment;

FIG. 37 is a front view showing the heat treatment apparatus accordingto the 18th embodiment;

FIG. 38 is an explanatory view showing a cross-sectional configurationof a heating coil according to the 18th embodiment;

FIG. 39 is an explanatory view showing a heat treatment apparatusaccording to a 19th embodiment of the present invention;

FIG. 40 is an explanatory view of a heat treatment apparatus accordingto a 20th embodiment of the present invention;

FIG. 41 is an explanatory view of a heat treatment apparatus accordingto a 21st embodiment of the present invention;

FIG. 42 is an explanatory view of a heat treatment apparatus accordingto a 22nd embodiment of the present invention; and

FIG. 43 is an explanatory view showing a heat treatment apparatusaccording to a 23rd embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Each embodiment according to the present invention will now be describedhereinafter. It is to be noted that arrows X, Y, and Z, in the drawingsrepresent three directions that are orthogonal to each other.Furthermore, structures are appropriately scaled up, scaled down, oromitted in each drawing for the purpose of illustration.

First Embodiment

An induction hardening apparatus and an induction hardening methodaccording to a first embodiment of the present invention will now bedescribed hereinafter with reference to FIG. 1 to FIG. 9. FIG. 1 is across sectional view showing a configuration of an induction hardeningapparatus 1 according to this embodiment, and FIG. 2 is a plan view. Asshown in FIG. 1 and FIG. 2, the induction hardening apparatus 1comprises a movement support unit (moving unit) that movably supports aworkpiece Q1 as a treatment object, respective heating devices 10A and10B arranged on the outer circumference of the workpiece Q1, and coolingunit 13 (cooling unit) that cools the workpiece Q1 after a heatingtreatment step for the workpiece Q1. The cooling unit 13 provided on thelower side is formed into a cylindrical shape to surround the outer sideof the workpiece Q1 that has moved to the lower side after the heatingtreatment, and it cools the workpiece Q1 arranged in an inner space 13a.

In this embodiment, for example, the cylindrical workpiece Q1 having astep is used, and a stepped outer peripheral surface of this workpieceis determined as a treatment target portion A.

The workpiece Q1 as an example of a treatment object is the steppedcylindrical member having an axis Q1 at the center, a concave portion Q1a that is recessed inward formed at the center in the axial direction,and a convex portion Q1 b that protrudes outward formed at both ends inthe axial direction. For example, here, there is employed the workpieceQ1 having a convex portion outside radius r1=1800 mm, a concave portionoutside radius r2=1780 mm, an inside radius r3=1700 mm, and a length h1in the axial direction (a first direction)=250 mm. It is to be notedthat an outside wall thickness δ1=100 mm and an inside wall thicknessδ2=80 mm.

The treatment target portion A that has an endless loop shape and iscircularly continuous is heated over the entire circumferential regionas a continuous direction of the loop by first heating devices 10A andsecond heating devices 10B arranged along a predetermined path aroundthe workpiece Q1 while rotating the workpiece Q1 on the axis C1.

In the treatment target portion A, an outer peripheral surface region ofthe concave portion Q1 a at the center in the axial direction isdetermined as a first region A1, and each of outer peripheral surfaceregions of the pair of convex portions Q1 b at both the ends in theaxial direction is determined as a second region A2. The first region A1and each second region A2 are apart from each other in the axialdirection of the treatment object, and they are also apart from eachother in the radial direction. The first region A1 is a circularstrip-like region having a length h2 in the axial direction=150 mm, andeach of the pair of second regions A2 is a circular strip-like regionhaving a length h3 in the axial direction=50 mm.

As shown in FIG. 2, the first heating devices 10A are arranged in thepath along the circumferential direction at four positions apart fromeach other at a center angle of 90 degrees. The second heating devices10B are arranged in the path along the circumferential direction at fourpositions apart from each other at the center angle of 90 degrees, andtwo second heating devices 10B are arranged in parallel along the axialdirection to cope with the pair of upper and lower convex portions Q1 bat each position.

The first heating devices 10A and the second heating devices 10B arealternately arranged to be apart from each other in the circumferentialdirection and the axial direction.

A first heating conductor portion 31A of the first heating device 10A isarranged to face the first region A1 while assuring a predetermined gapdimension G1. The first heating device 10A inductively heats the firstregion A1 in the treatment target portion A on the outer periphery ofthe workpiece Q1 in an intensive manner. A heating conductor portion 31Bof the second heating apparatus 10B is arranged to face the secondregion A2 while assuring a predetermined gap dimension G2. The secondheating device 10B inductively heats the second region A1 in anintensive manner.

In this embodiment, a circumferential direction R along the outerperipheral surface of the workpiece Q1 with the axis C1 at the center isdetermined as a second direction, and the Z direction as the axialdirection of the workpiece Q1 is determined as a first direction. It isto be noted that since the workpiece Q1 has the stepped shape, a radialdimension in the circumferential direction R of the first heatingconductor portion is different from that of the second heating conductorportion, but the workpiece Q1 moves along both the circumferentialdirections when rotated on the axis C1. The paths including thecircumferential directions R1 and R2 are defined as moving paths, and arotational direction including R1 and R2 with C1 at the center isdetermined as a second direction R. A radius of the circumferentialdirection R1 is a value obtained by adding the gap dimension G1 to aradial dimension r2 which is an outside diameter dimension of theconcave portion Q1 a, and it is r2+G1. A radius of the circumferentialdirection R2 is a value obtained by adding the gap dimension G2 to aradial dimension r1 which is an outside diameter dimension of the convexportion Q1 b, and it is r1+G1.

As shown in FIG. 1 to FIG. 4, each of the first heating devices 10A andthe second heating devices 10B has a high-frequency power supply 21 aspower supplying unit, lead wires 22 and 23 connected to thehigh-frequency power supply 21, a spacer 28 including a pair ofconductive plates 24 and 25 connected to the lead wires 22 and 23, aninduction heating coil 26 having both ends connected to the pair ofconductive plates 24 and 25, and a core 27 arranged on a back side ofthe heating conductor portion 31A or 31B of the induction heating coil26.

The induction heating coil 26 of the heating device 10A continuously andintegrally includes the zigzag heating conductor portion 31A facing thefirst region A1 of the workpiece Q1, a first connection conductorportion 32 continuous with one end side 31 a of the heating conductorportion 31A, and a second connection conductor portion 33 continuouswith the other end side 31 b of the heating conductor portion 31A.

As shown in FIG. 4 the heating conductor portion 31A of the firstheating device 10A has a zigzag shape such that U-shaped bent portions34 and 35 are opened toward the center in the Z direction andalternately continuously arranged along the circumferential direction Rso that these bent portions face each other. The bent portion 34 has aU-like shape opened toward the lower side, and the bent portion 35 has alike snare shape opened toward the upper side. An interval R5 betweenthe coils adjacent to each the is set to be not less than one times andnot greater than two times a dimension of R4 as a coil width. Here,example, a total of the dimensions L1 of the our heating conductorportions 31A in the second direction is set to approximately 1/3 of adimension of the whole circumference in the second direction of thefirst region A1. That is, a cover ratio as a ratio of the dimension ofthe second direction of one heating conductor portion 31A to the firstregion A1 is set to 1/12, and a central angle α1 is set to 30 degrees.

As shown in FIG. 5 and FIG. 6, the induction heating coil 26 of thesecond heating device 10B continuously and integrally includes ahairpin-like heating conductor portion 31B that faces the second regionA2 of the workpiece Q1, a first connection conductor portion 32 that iscontinuous with one end side 31 a of the heating conductor portion 31B,and a second connection conductor portion 33 that is continuous with theother end side 31 b of the heating conductor portion 31B. When seen fromthe front side, the heating conductor portion 31B is bent into arectangular frame shape from the one end side 31 a on the left side inFIG. 6, the other end side 31 b is configured to return to the lowerside of the one end side 31 a in the drawing, and the heating conductorportion 31 is continuous with the connection conductor portions 32 and33 at both the ends 31 a and 31 b on the left side in the drawing. It isto be noted that a cover ratio of the second heating device 10B is notnecessarily set to the same value as that of the first heating device10A, and it is changed in accordance with a shape of the workpiece.

In each of the heating devices 10A and 10B, the first connectionconductor portion 32 and the second connection conductor portion 33 arearranged to sandwich the spacer 28 therebetween. The spacer 28 isconstituted by overlapping the pair of conductive plates 24 and 25 eachhaving a rectangular tabular shape and a rectangular tabular insulatingplate 38 sandwiched between the pair of conductive plates 24 and 25 andfixing the conductive plates 24 and 25 and the insulating plate 28through insulating bushes 39 by bolts 41 and nuts 42. The respectiveconductive plates 24 and 25 are connected to the high-frequency powersupply 21 through the lead wires 22 and 23. Couplers 36 and 36 (only onecoupler is shown) configured to connect a component such as a hose for acoolant are provided at end portions of the first connection conductorportion 32 and the second connection conductor portion 33.

As shown in a cross-sectional view of FIG. 7, the induction heating coil26 is formed into a rectangular hollow shape from a material such ascopper. This hollow portion 26 a serves as a path through which thecoolant circulates. The core 27 is made of a material having highpermeability such as a silicon steel sheet, a polyiron core, orFERROTRON and arranged on the back sides of the heating conductorportions 31A and 31B. The core 27 is formed into a shape having aU-shaped cross section that integrally includes both side portions ofeach of the heating conductor portions 31A and 31B and a rear wallportion.

A movement support unit 11 depicted in FIG. 1 has a function ofrotationally moving the workpiece Q1 on the axis C1 in a state that theworkpiece Q1 is set at a predetermined position. At this time, themovement support unit 11 performs control so that the gap dimension G1between the heating conductor portion 31A and the first region A1 can bemaintained at a predetermined value and the gap dimension C2 between theheating conductor portion 31B and the second region A2 can be maintainedat a predetermined value.

As descried above, the first heating conductor portion 31A and thesecond heating conductor portion 31B have shapes different from eachother and are apart from each other in the axial direction, and sizes,shapes, and positions of the respective regions A1 and A2 are alsodifferent from each other. Therefore, as shown in FIG. 8, a firstheating region P1 formed with the central part of the concave portion Q1a in the Z direction at the center and a second heating region P2 formedwith the center of each of the pair of upper and lower convex portionsQ1 b at the center are heating regions different in the axial direction.

An induction hardening method according to this embodiment will now bedescribed. The induction hardening method according to this embodimentis constituted of a moving and heating step of relatively moving thetreatment target portion A and the heating conductor portions 31A and31B while heating the treatment target portion A and a cooling step ofcooling the treatment target portion A after the moving and heatingstep.

At the moving and heating step, the first region A1 as a part of thetreatment target portion A is arranged to face the first heatingconductor portion 31A, the second region A2 that is at least a part ofthe treatment target portion A is arranged to face the second heatingconductor portion 31B having the second heating region P2 different fromthe first heating region P1 provided by the first heating conductorportion 31A and the regions A1 and A2 are relatively moved with respectto the first heating conductor portion 31A and the second heatingconductor portion 31B along the predetermined second direction R whileheating the treatment target portion A by the first heating conductorportion 31A and the second heating conductor portion 31B.

Specifically, when the high-frequency power supply 21 is turned on in astate that the heating conductor portions 31A and 31B face the first andsecond regions A1 and A2, a high-frequency current flows through thelead wire 22, the first conductive plate 24, the first connectionconductor portion 32, the heating conductor portion 31, the secondconnection conductor portion 33, the second conductive plate 25, and thelead wire 23 in the mentioned order and returns to the high-frequencypower supply 21. At this time, in the heating conductor portions 31A and31B, the high-frequency current flows from the one end is side towardthe other end 31 b side, and an induction current is generated onsurfaces of the heating conductor portions 31A and 31B to inductivelyheat the oppositely arranged regions A1 and A2. Then, the heating iscarried out simultaneously at positions apart from each other by a fixeddistance in the axial direction and the radial direction. That is, theopposed surface of the workpiece Q1 is subjected to a heating treatmentat the respective positions apart from each other.

When the workpiece Q1 is rotated on the axis C1 in a state that each ofthe gap dimensions G1 and G2 is maintained at a predetermined value bythe movement support unit 11 while performing this heating treatment,the treatment target portion A is relatively moved with respect to theheating conductor portions 31A and 31B along the second direction R at apredetermined speed. For example, here, the relative movement iseffected at a speed of 200 to 300 mm/sec while maintaining a power of100 to 150 kW and the gap dimension G1 or G2=2.5 mm.

Based on this moving and heating step, a first heat treatment using thefirst heating conductor portion and second heating using the secondheating conductor portion are sequentially carried out in each region ofthe treatment target portion A. Here, when the workpiece Q1 is rotated90 degrees, the first and second heating processes are carried out withrespect to the whole circumference of the treatment target portion A.The respective heating regions P1 and P2 of the treatment target portionA heated by the heating conductor portions 31A and 31B form onecontinuous heating region P3. Therefore, as shown in FIG. 8 and FIG. 9,the first and second heating regions P1 and P2 are combined, and theheat treatment is performed in the desired third heating region 23.

Then, after the moving and heating step for the entire stroke in thesecond direction of the treatment target portion, the movement supportunit 11 moves the workpiece Q1 to the lower cooling unit 13 along theaxial direction. The cooling unit 13 uses the coolant to cool theworkpiece Q1 arranged in the space 13 a that is a cooling regionsurrounded by a cooling jacket (a cooling step).

According to the induction heating coil, the induction hardeningapparatus, and the induction hardening method of this embodiment, thefollowing effects can be obtained.

According to the embodiment, when the heating conductor portions 31A and31B are combined to perform the heat treatment, the heating regionsprovided at different positions can be combined to obtain one continuousheating region, and hence the heat treatment for the desired heatingregion can be realized with the simple configuration. When the treatmenttarget portion has a complicated shape, the uniform desired heattreatment can be likewise realized with the simple configuration.

Further, since the first heating conductor portion 31A that heats thefirst region A1 which is a region large in the axial direction is formedinto the zigzag shape continuously having bent portions, a ferromagneticfield can be assured, and a good temperature pattern can be obtained.Therefore, the high-speed uniform heat treatment can be performed with asmall amount of power. When the heating conductor portion 31 having thezigzag shape according to this embodiment is used, the heat treatmentcan be realized with a speed of 200 to 300 mm/sec and a heating time=300s in a case of achieving an end-point temperature of 850 degrees on thesurface of the first region A1 with the power of 100 kW. That is, whenthe induction heating coil 26 having the zigzag heating conductorportion 31 is used, for example, it is possible to realize the heattreatment for a large workpiece based on scanning partial heating thatcannot be realized by the hairpin-like induction heating coil associatedwith the first region A1. For example, although the coil efficiency is30 to 40% in planar (end face) heating using the hairpin-like inductionheating coil, the coil efficiency exceeds 70% in the zigzag inductionheating coil.

Further, using such a high-efficiency heating coil enables the uniformheat treatment having no soft zone at a start end and a termination endof the treatment when the treatment target portion A has a loop-likeshape. Therefore, for example, if a roller bearing is a workpiece and araceway surface on which a rolling element passes is the treatmenttarget portion A, a uniform hardened layer with no soft zone can beformed, thereby obtaining particularly excellent characteristics.

Since the heating treatment is carried out while arranging the heatingdevices to face a part of the treatment target portion A alone andeffecting the relative movement, a size of the heating conductor portion31 can be decreased even though the treatment target portion A and theworkpiece Q1 are large, and the respective heating devices 10A and 10Bcan be reduced in size. Therefore, the necessary power can be reduced,and a manufacturing cost can be decreased.

Further, since the heating treatment is carried out while arranging theheating devices to face a part of the treatment target portion A aloneand effecting the relative movement, for example, when a circular memberhaving a bent portion is a workpiece, appropriate gap dimensions can beeasily maintained even though the workpiece is deformed due to a factorsuch as thermal expansion. For example, in the case of using an annularinduction heating coil associated with a circular treatment targetportion to perform the heat treatment adopting a single shot heatingprocess, since the workpiece is deformed due to the thermal expansion,the induction heating coil must be set to be larger in advance, andhence a problem of poor heating efficiency occurs, but appropriate gapscan be maintained by just adjusting the arrangement with respect to theworkpiece when a cover ratio is small, as in this embodiment.

Second Embodiment

An induction hardening apparatus 2 according to a second embodiment ofthe present invention will now be described with reference to FIG. 10and FIG. 11. It is to be noted that elements other than shapes of aworkpiece Q2 and a heating conductor portion 31 are equal to those inthe first embodiment to omit a repeated explanation. It is to be notedthat the workpiece Q2 has a cylindrical shape having an annular planeportion.

FIG. 10 is a plan view showing an arrangement of the induction hardeningapparatus 2 according to this embodiment, and FIG. 11 is en explanatoryview showing a shape of the heating conductor portion 31 in theinduction hardening apparatus 2.

In this embodiment, as shown in FIG. 10, each of upper and lower endsurfaces of the workpiece Q2 has a planar cylindrical shape, and eachend surface is determined as a treatment target portion A. Further, theheating conductor portion 31 of a first heating device 10A is formedinto a zigzag shape such that bent portions 134 and 135 are alternately,continuously, and oppositely arranged along a circumferential directionR and each bent conductor portion 136 is arranged between the bentportions 134 and 135 facing each other. Each of the bent portions 134 isformed into a bent shape opened toward the outer site which is one sidein a direction crossing a moving direction, and each bent portion 135 isformed into a bent shape opened toward the inner side in the radialdirection which is the other side of the same.

As shown in FIG. 10 and FIG. 11, each of the conductor portions 136 isextended to cross the circumferential direction R, configured in such amanner that a circumferential length of a part apart from an axis C1which is the center of rotation is longer than a circumferential lengthof a part close to the same, and formed in such a manner that a lengthin the circumferential direction can be associated with a speed in thecircumferential direction. Since the conductor portion 136 is bent insuch a manner that an extension angle of the hart apart from the axis C1with respect to the circumferential direction R is smaller than anextension angle of the part close to the axis C1 while maintaining across-sectional area and a cross-sectional share orthogonal to anextending direction constant, the speed and the length in thecircumferential direction can be associated with each other.

In this embodiment, each of the conductor portions 136 is sectioned intothree parts in the radial direction, and a center line C2 of theconductor portion 136 is bent at an angle of α1=α2=150 degrees atrespective boundaries between the parts adjacent to each other. Thiscenter line is parallel to the extending direction of each part. A firstpart 136 a on the inner side in the radial direction forms an angle ofθ1=90 degrees with respect to the circumferential direction R, anintermediate second part 136 b is inclined to form an angle of θ2=60degrees with respect to the circumferential direction R, and theoutermost third part 136 c is inclined to form an angle or θ3=30 degreeswith respect to the circumferential direction R. That is, θ1>θ2>θ3 isachieved.

For example, here, dimensions are set based on two positions, i.e., theinnermost point P1 and the outermost point P3 of the workpiece. Assumingthat r4 is a radius of rotation (a distance from the center of axis C1)of the reference point P1 on the treatment target portion A1 facing thefirst part 136 a, r5 is a radius of rotation (a distance from the centerof axis C1) of the reference point 23 on the treatment target portion A1facing the third part 136 c, L1 is a circumferential dimension of thefirst part 136 a facing P1, and L3 is a circumferential dimension of thethird part 136 c facing P3, the conductor portion 136 is set toL1:L3≈r4:r5, and the distance from the axis C1 as the center of rotationis associated with the circumferential dimension. In this case, based onP1 and P3, the circumferential dimension (the distance) is inverselyproportionate to a circumferential speed which is proportionate to theradius of rotation, and a time required for passage, i.e., a heatingtime is maintained constant. Further, a dimension L1 of the middlesecond part 136 b is set to achieve L1<L2<L3 so that L2 becomes adimension between L1 and L3.

This embodiment can obtain the same effect as that of the firstembodiment. Moreover, the induction hardening apparatus 2 according tothis embodiment is set so that a dimension of the heating conductorportion 31 in the moving direction becomes large on the outer peripheralside where a speed of the workpiece Q2 cutting across and passing theheating conductor portion 31 when the workpiece Q2 is rotated on theaxis C1 is increased rather than on the inner side where this speed isreduced, and hence a time required for passage can be made uniform, anda heat treatment time is also made uniform.

Third Embodiment

An induction hardening apparatus 2 according to a third embodiment ofthe present invention will now be described with reference to FIG. 12.It is to be noted that structures are equal to those in the foregoingembodiments except that a shape of a workpiece Q3 is different and aheating conductor portion 31 is parallel to an inclined surface of theworkpiece Q3, thereby omitting a repeated explanation.

Since a plan view of the induction hardening apparatus 2 is equal toFIG. 10 and a plan view of the heating conductor portion 31 is equal toFIG. 11, these views will be omitted.

In this embodiment, as shown in FIG. 12, the workpiece Q3 has adrum-like shape such that upper and lower outer peripheral surfaces areinclined, and the outer peripheral surfaces are determined as atreatment target portion A. The inclined upper outer peripheral surfaceof the workpiece Q3 is determined as a first region A1, and the inclinedlower outer peripheral surface is determined as a second region A2. Aninduction hardening apparatus 3 according to this embodiment comprises afirst heating device 10A that inductively heats the first region A1 onthe upper surface and a second heating device 10A that inductively heatsthe second region A2 on the lower surface.

Respective heating conductor portions 31A according to this embodimentare inclined with respect to the axial direction and the circumferentialdirection, and they are configured along the upper and lower outerperipheral surfaces of the workpiece Q3.

As shown in FIG. 10, a heating conductor portion 31A of the firstheating device 10A has a zigzag shape in which bent portions 134 and 135are alternately continuously arranged in opposed directions along thecircumferential direction R and each bent conductor portion 136 isarranged between the bent portions 134 and 135 facing each other. Eachof the bent portions 134 forms a bent shape opened toward the outer sidewhich is one side of a direction crossing the moving direction, and thebent portion 136 forms a bent shape opened toward the radially innerside which is the other side of the same. Each of the conductor portions136 is constituted in such a manner that a circumferential length of aportion apart from the axis C1 which is the center of rotation becomeslonger a circumferential length of a portion close to the axis C1, andit is formed in such a manner that the length in the circumferentialdirection is associated with a speed in the circumferential direction.Since the conductor portion 136 is bent in such a manner that anextension angle of the part apart from the axis C1 with respect thecircumferential direction R is smaller than an extension angle of thepart close to the axis C1 while maintaining a cross-sectional area and across sectional shape orthogonal to en extending direction constant, thespeed and the length in the circumferential direction can be associatedwith each other.

This embodiment can obtain the same effect as the first embodiment.

Fourth Embodiment

An induction hardening apparatus 3 according to a fourth embodiment ofthe present invention will now be described hereinafter with referenceto FIG. 13. FIG. 13 is an explanatory view showing an arrangement of aninduction hardening apparatus according to this embodiment. It is to benoted that structures other than a shape of a workpiece Q4 are equal tothose in the second embodiment, thereby omitting a repeated explanation.The workpiece Q4 has a hollow shape and inner peripheral surfacesinclined with respect to the axial direction and the circumferentialdirection.

Respective heating conductor portions 31A according to this embodimentare all inclined in the axial direction and the circumferentialdirection, and they are constituted along the upper and lower innerperipheral surfaces of the workpiece Q4.

As shown in FIG. 10, the heating conductor portion 31A of a firstheating device 10A forms a zigzag shape in which bent portions 134 and135 are alternately continuously arranged in opposed directions alongthe circumferential direction R and each bent conductor portion 136 isarranged between the bent portions 134 and 135 facing each other. Eachof the bent portions 134 forms a bent shape opened toward the outer sidewhich is one side of a direction crossing the moving direction, and thebent portion 135 forms a bent share opened toward the radially innerside which is the other side of the same. Each of the conductor portions136 is extended to cross the circumferential direction R, constituted insuch a manner that a circumferential length of a portion apart from theaxis C1 which is the center of rotation becomes longer than acircumferential length of a portion close to the axis C1, and formed insuch a manner that the length in the circumferential direction isassociated with a speed in the circumferential direction. Since theconductor portion 136 is bent in such a manner that an extension angleof the part apart from the axis C1 with respect to the circumferentialdirection R is smaller than an extension angle of the part close to theaxis C1 while maintaining a cross-sectional area and a cross-sectionalshape orthogonal to an extending direction constant, the speed and thelength in the circumferential direction can be associated with eachother.

This embodiment can obtain the same effect as the first embodiment.

Fifth Embodiment

An induction hardening apparatus 4 according to a fifth embodiment ofthe present invention will now be described with reference to FIG. 14.It is to be noted that structures are equal to those in the firstembodiment except that a shape of a workpiece Q5 is different and atreatment target portion A is inclined, thereby omitting a repeatedexplanation.

FIG. 14 is a side view showing an arrangement of the induction hardeningapparatus 4 according to this embodiment.

In this embodiment, as shown in FIG. 14, a peripheral surface of theworkpiece Q5 having a stepped trapezoidal cross section is determined asa treatment target portion A. An outer peripheral surface of a centralpart in the axial direction is determined as a first region A1, and anouter peripheral surface of each step portion protruding toward theouter side at each of both ends in the axial direction is determined asa second region A1.

The induction hardening apparatus 4 comprises a first heating apparatus10A that inductively heats the first treatment target portion A1 at thecentral part in the axial direction and second heating devices 10B thatinductively heats the second treatment target portions A2 provided attwo positions at both the ends in the axial direction. Each of theregions A1 and A2 forms a surface inclined with respect to the axis, anda distance from the center of rotational movement is changed. Heatingconductor portions 31A and 31B according to this embodiment are allinclined with respect to the axial direction and the circumferentialdirection, and they are constituted in parallel to the upper and lowerouter peripheral surfaces of the workpiece Q5. As a shape of the heatingconductor portion 31A, for example, the same heating conductor portion31A as that in the third embodiment is used. That is, the heatingconductor portion is inclined in the axial direction and has a zigzagshape with bent portions 134 and 135 facing each other, and a conductorportion 136 is bent in such a manner that an extension angle of a partapart from the axis C1 with respect to the circumferential direction Ris smaller than an an extension angle of a part close to the axis C1while maintaining a cross-sectional area and a cross-sectional shapeorthogonal to an extending direction constant.

This embodiment can obtain the same effects as as those in the first tofourth embodiments.

Although the flexure portions are exemplified by the bent portions 34and 35 each of which is bent into a rectangular shape having a U-likecross section in the foregoing embodiment, the present invention is notrestricted thereto.

Sixth Embodiment

In FIG. 15, a first heating conductor portion 31C configured to havecurved portions (the flexure portions) 34 and 35 each having a shapecurved into a semicircular shape may be applied as a sixth embodiment ofthe present invention. This embodiment can likewise obtain the sameeffects as those in the first to fifth embodiments.

Seventh Embodiment

In FIG. 16, a first heating conductor portion 31D configured to havebent portions 34 and 35 bent into a trapezoidal shape may be applied asa seventh embodiment of the present invention. This embodiment canlikewise obtain the same effects as those in the first to fifthembodiments.

Moreover, a zigzag shape like the first embodiment may be adopted inplace of such a bent shape. Although the example where the relativemovement is carried out by rotating the workpiece Q1 has been explainedin the foregoing embodiment, the present invention is not restrictedthereto, and the relative movement may be effected by moving the heatingconductor portions 31A and 31B.

Eighth Embodiment

Although the example where each of the first heating device 10A and thesecond heating device 10B is arranged at four positions has beendescribed in the first to fifth embodiments, the present invention isnot restricted thereto.

FIG. 17 schematically shows a positional relationship when two firstheating devices 10A and two second heating devices 10B are arranged asan eighth embodiment of the present invention. This embodiment canlikewise obtain the same effects as those in the first to fifthembodiments.

Ninth Embodiment

FIG. 18 schematically shown a positional relationship when three firstheating devices 10A and three second heating devices 10B are arranged asa ninth embodiment of the present invention. This embodiment canlikewise obtain the same effects as those in the first to fifthembodiments.

10th Embodiment

FIG. 19 schematically shows a positional relationship when five firstheating devices 10A and five second heating devices 10B are arranged asa 10th embodiment of the present invention. This embodiment can likewiseobtain the same effects as those in the first to fifth embodiments.

11th Embodiment

FIG. 20 schematically shows a positional relationship when six firstheating devices 10A and six second heating devices 10B are arranged asan 11th embodiment of the present invention. This embodiment canlikewise obtain the same effects as those in the first to fifthembodiments.

12th Embodiment

Although the coil arrangement has been exemplified by the alternatearrangement or the opposed arrangement, the present invention is notrestricted thereto, and an arbitrary arrangement such as 1:3 can beadopted. Although the workpiece Q1 having one step has been described asthe example in the foregoing embodiment, the present invention is notrestricted thereto, and the present invention can be likewise applied toa cage in which a workpiece having two or more steps is a target.

In FIG. 21, as a 12th embodiment according to the present invention,when a workpiece Q5 having two steps is a target, three regions, i.e.,first to third regions A1, A2, and A3 are set in a treatment targetportion A which is an outer peripheral surface of the workpiece inaccordance with positions of the steps. It is to be noted that theworkpiece Q5 is symmetrical in the vertical direction and has the upperand lower steps in this example, and hence each of the second region A2and the third region A3 is provided at two positions in the axialdirection. Here, three induction hardening devices, 10A, 10B, and 10Care used and heating conductor portions 31A, 31B, and 31C are arrangedto face the regions A1, A2, and A3, respectively. In this case, like theforegoing embodiments, when a first heating region P4 heated by theheating conductor portion 31A, a second heating region P5 heated by theheating conductor portion 31B, and a third heating region P6 heated bythe heating conductor portion 31C are combined, one desired continuousheating region P7 can be easily treated.

Further, the workpiece is not restricted to the hollow type, and it maybe a solid type.

13th Embodiment

An induction hardening apparatus 201 (a heat treatment apparatus)according to a 13th embodiment of the present invention will now bedescribed with reference to FIG. 22 to FIG. 26.

FIG. 22 is an explanatory view schematically showing an entireconfiguration of the induction hardening apparatus 201 according to thisembodiment. As shown in FIG. 22, the induction hardening apparatus 201is an apparatus that performs high-frequency hardening, and it comprisesa movement support unit (a workpiece moving and rotating supportplatform) 211 that movably supports a workpiece W1 as a treatmentobject, an induction heating device 210 (a heat treatment device) theinductively heats a treatment target portion N1 of the workpiece W1, anda cooling unit 213 (cooling unit) for cooling the workpiece W1 after aheat treatment step for the treatment target portion N1. The inductionheating device 210 has a built-in matching board connected to ahigh-frequency power supply 221. The movement support unit 211 rotatesthe workpiece W1 on an axis C1 in a rotation direction (acircumferential direction) in a state such that the workpiece W1 is setat a predetermined position. At this time, the movement support unit 211performs control to maintain a gap dimension J1 between a heatingconductor portion 231 and the workpiece W1 at a predetermined value.Further, after the end of a heat treatment performed over the wholecircumference (the whole stroke) of the treatment target portion N1, themovement support unit 211 moves the workpiece 1 to the cooling unit 213.The cooling unit 213 cools the workpiece W1 after the end of the heattreatment.

As shown in FIG. 23 to FIG. 26, the induction heating apparatus 210comprises the high-frequency power supply 221 as power supplying unit,lead wires 222 and 223 connected to the high-frequency power supply 221,a spacer 228 including a pair of conductive plates 224 and 225 connectedto the lead wires 222 and 223, an induction heating coil 226 having bothends connected to the pair of conductive plates 224 and 225, and a core227 (shown in FIG. 26 alone) arranged on a back side of the heatingconductor portion 231 of the induction heating coil 226.

As shown in FIG. 22, the workpiece W1 as an example of the treatmentobject is a radially thick component having a thickness of 25 mm orabove, and this example uses a cylindrical member having, e.g., anoutside diameter d1=500 mm, an inside diameter d2=250 mm, and an axiallength h1=100 mm with the axis C1 at the center.

In this embodiment, for example, an annular planar region of theworkpiece W1 orthogonal to the axis C1, which is one end surface in theaxial direction, is determined as a treatment target portion N1. Thetreatment target portion N1 has an endless loop-like shape that iscontinuous along she circumferential direction of the workplace W1.Here, description will be given as to a case in which, in a state thatthe heating conductor portion 231 is arranged to face a part of thetreatment target portion N1, the workpiece W1 is rotated on the axis C1by the movement support unit 211, whereby the treatment target portionN1 is relatively moved with respect to the heating conductor portion 31along the circumferential direction R (a rotation direction) with theaxis C1 at the canter and a heat treatment is performed with respect tothe whole circumference of the treatment target portion N1.

As shown in FIG. 22 and FIG. 23, the induction heating coil 226continuously and integrally comprises a zigzag-shaped heating conductorportion 231 that faces a part of the treatment target portion N1 of theworkplace W1, a first connection conductor portion 232 that iscontinuous with one end side 231 b of the heating conductor portion 231,and a second connection conductor portion 233 that is continuous withthe other end side 231 a of the heating conductor portion 231. The firstconnection conductor portion 232 is extended to be continuous with theend portion 231 b on one end side of the heating conductor portion 231,and a coupler 237 configured to connect a component such as a hose for acoolant is provided at an end of this portion 232. The second connectionconductor portion 233 is extended to be continuous with the end portion231 a on the other end side of the heating conductor portion 231, and acoupler 237 configured to connect a component such as a hose for acoolant is provide at an end portion of this portion 233.

The first connection conductor portion 232 and the second connectionconductor portion 233 are arranged to sandwich a spacer 228. The spacer228 has a configuration such that a pair of conductive plates 224 and225 each having a rectangular tabular shape and a rectangular tabularinsulating plate 238, which is sandwiched between the pair of conductiveplates 224 and 225, are arranged in an overlapping manner and theconductive plates 224 and 225 and the insulating plate 238 are fixed bybolts 241 and nuts 242 through insulating bushes 239. The respectiveconductive plates 224 and 225 are connected to the high-frequency powersupply 221 through the lead wires 222 and 223.

As shown in FIG. 23 to FIG. 25, the heating conductor portion 231 has azigzag shape such that bent portions 234 and 235 are continuouslyalternately arranged in opposed directions along the circumferentialdirection R and each bent portion 236 is arranged between the bentportions 234 and 235 facing each other. Each of the bent portions 234has a bent shape opened toward the outer side which is one side in adirection crossing the moving direction, and each bent portion 35 has abent shape opened toward the radially inner side which is the otherside.

A dimension in the circumferential direction R of the heating conductorportion 231 in which the bent portions 234 and 235 and the conductorportions 236 coupling these portions are configured is set to a coverratio of 1/3, which is a ratio of the dimension in the circumferentialdirection R of the heating conductor portion 231 to the wholecircumference of the treatment target portion N1, and also set to acentral angle β1=120 degrees, for example.

Each of the conductor portions 236 is extended to cross thecircumferential direction R, configured in such a manner that acircumferential length of a part apart from the axis C1 which is thecenter of rotation is longer than a circumferential length of a partclose to the same, and formed in such a manner that a length in thecircumferential direction can be associated with a speed in thecircumferential direction. Since the conductor portion 236 is bent insuch a manner that an extension angle of the part apart from the axis C1with respect to the circumferential direction R is smaller than anextension angle of the part close to the axis C1 while maintaining across-sectional area and a cross-sectional shape orthogonal to anextending direction constant, the speed and the length in thecircumferential direction can be associated with each other.

In this embodiment, as shown in FIG. 25, each of the conductor portions236 is sectioned into three parts in the radial direction, and a centerline C2 of the conductor portion 236 is bent at en angle of α1=α2=150degrees at respective boundaries between the parts adjacent to eachother. This center line is parallel to the extending direction of eachpart. A first part 236 a on the inner side in the radial direction formsan angle of θ1=90 degrees with respect to the circumferential directionR, an intermediate second part 236 b is inclined to form an angle ofθ2=60 degrees with respect to the circumferential direction R, and theoutermost third part 236 c is inclined to form an angle of θ3=30 degreeswith respect to the circumferential direction R. That is θ1>θ2>θ3 isachieved.

For example, here, dimensions are set based on two positions, i.e., theinnermost point P1 and the outermost point P3 of the workpiece. It isassumed that a radius of rotation (a distance from the center of axisC1) of the reference point P1 on the treatment target portion N1 facingthe first part 236 a is r1=250 mm, a radius of rotation (a distance fromthe center of axis C1) of the reference point P3 on the treatment targetportion N1 facing the third part 236 c is r3=500 mm, a circumferentialdimension of the first part 236 a facing P1 is M1=15 mm, and acircumferential dimension of the third part 236 c facing P3 is M3=30 mm.That is, the conductor portion 236 is set to achieve M1:M3≈r1:r3, andthe distance from the center of axis C1 as the center of rotation isassociated with the circumferential dimension. Therefore, based on P1and P3, the circumferential dimension (the distance) is inverselyproportionate no a circumferential speed which is proportionate to theradius of rotation, and a time required for passage, i.e., a heatingtime is maintained constant. Further, a dimension M2 of the middlesecond part 236 b is set to achieve M1<M2<M3 so that M2 becomes adimension between M1 and M3.

That is the dimension of the heating conductor portion 231 in the movingdirection is set to be larger on the outer peripheral side where a speedof the treatment target portion N1 cutting across and passing theheating conductor portion 231 is increased than on the inner side wherethe speed is reduced when the workplace W1 is rotated on the axis C1,thereby making a heat treatment time uniform.

As shown in a cross-sectional view of FIG. 26, the induction heatingcoil 226 is formed into a rectangular hollow shape from a material suchas copper. This hollow portion 226 a serves as a path through which thecoolant circulates. The core 227 is made of a material having highpermeability such as a silicon steel sheet, a polyiron core, orFERROTRON and arranged on the back side of the heating conductor portion231. The core 227 is formed into a shape having a U-shaped cross sectionthat integrally includes both side portions of the heating conductorportion 231 and a rear wall portion.

An induction hardening method (a heat treatment method) according tothis embodiment will now be described. The induction hardening methodaccording to this embodiment is constituted of a moving and heating stepof performing relative movement while heating the treatment targetportion N1 and a cooling step of cooling the treatment target portion N1after the moving and heating step.

At the moving and heating step, as shown in FIG. 22 to FIG. 25, when thehigh-frequency power supply 221 is turned on in a state that the beering conductor portion 231 faces a part of the treatment target portionN1, a high-frequency current flows through the lead wire 222, the firstconductive elate 224, the first connection conductor portion 232, theheating conductor portion 231, the second connection conductor portion233, the second conductive plate 225, and the lead wire 223 in thementioned order and returns to the high-frequency power supply 221.

In the heating conductor portion 231, as indicated by arrows in thedrawing, the high-frequency current flows from the one end 231 b sidetoward the other end 231 a side through the bent portions 234, theconductor portions 236, and the bent portions 235, and an inductioncurrent is generated on a surface of the heating conductor portion 231to inductively heat the oppositely arranged treatment target portion N1.

When the workplace W1 is rotated in a state that a gap dimension J1between the surface of the treatment target portion N1 of the workplaceW1 and the surface of the heating conductor portion 231 is maintained ata predetermined value by the movement support unit 211, the treatmenttarget portion N1 is relatively moved with respect to the heatingconductor portion 231 along the circumferential direction at apredetermined speed.

For example, here, the relative movement is effected at a speed of 200to 300 mm/sec while maintaining a power of 100 to 150 kW and the gapdimension J1=2.5 mm. When the workplace W1 is rotated, it is possible touniformly heat the entire region of the treatment target portion N1which is the annular region on the end surface of the workpiece W1arranged to face the heating conductor portion 231.

Here, considering the degree of the heat treatment at the referencepoints P1, P2, and P3 of the conductor portion 236, a time required topass the opposed treatment target portion N1 is maintained constant eventhough the circumferential speed differs at each of the reference pointsP1, P2, and P3. Therefore, the degree of heating applied to thetreatment target portion N1 can be made uniform.

Then, after the moving and heating step for the entire stroke in thecircumferential direction R of the treatment target portion, themovement support unit 211 moves the workpiece W1 to the lower coolingunit 213 along the axial direction. The cooling unit 213 uses thecoolant to cool the workplace N1 arranged in a space 213 a that is acooling region surrounded by a cooling jacket (a cooling step).

Further, when the coolant flows through the hollow portion 226 a in theinduction heating coil 226 via the first connection conductor portion232, the heating conductor portion 231, and the second connectionconductor portion 223, the induction heating coil 226 and the conductiveplates 224 and 225 are cooled.

According to the induction heating coil, the induction heatingapparatus, and the induction heating method according to thisembodiment, the following effect can be obtained. That is, since theconductor portion 236 of the heating conductor portion 231 is changed insuch a manner that the dimension in the circumferential direction can beassociated with the distance from the axis C1, a time required forpassage is maintained constant, and hence a heating time is madeuniform. Therefore, a uniform treatment can be realized even though amovement speed of each part differs due to the rotation. Further, aheating temperature can be readily made uniform by the simpleconfiguration, i.e., just bending at the angle associated with thecircumferential speed with a fixed cross-sectional area withoutcomplicating heat treatment conditions.

Since the heating conductor portion 231 has a zigzag shape continuouslyhaving oppositely arranged bent portions, a ferromagnetic field can beassured, and an excellent temperature pattern can be obtained.Therefore, the high-speed and uniform heat treatment can be performedwith less power. When the zigzag heating conductor portion 231 accordingto this embodiment is used, the heat treatment can be realized with aspeed of 200 to 300 mm/sec and a heating time=300 s in a case ofachieving an end-point temperature of 850 degrees on the surface of thetreatment target portion N1 with the power of 100 kW. Therefore, whenthe workpiece has a large diameter of approximately 3.5 m, heatingexceeding a transformation point A3 can be realized with a cover ratioof approximately 1/3.

When the induction heating coil 226 having the zigzag heating conductorportion 231 is used, the heat treatment for a large workpiece can berealized based on the scanning partial heating that cannot be realizedby, e.g., a tabular induction heating coil. Further, since a treatmentspeed can be increased in this manner, the treatment can be carried outin accordance with a procedure of first effecting the heat treatmentwhile moving the entire treatment target portion N1 and then performingcooling. Therefore, even the partial heating can realize the uniformheat treatment with no soft zone at a start end and a termination end ofthe treatment even though the treatment target portion N1 has a loopshape.

Since the heat treatment is performed while facing a part of thetreatment target portion N1 and effecting the relative movement, a sizeof the heating conductor portion 231 can be decreased even though thetreatment target portion N1 and the workpiece W1 are large, and theentire induction heating apparatus 210 can be reduced in size.Therefore, necessary power can be reduced, and a manufacturing cost canbe suppressed.

Moreover, since the heat treatment is carried out while facing a part ofthe treatment target portion N1 alone and performing the relativemovement, even if the workplace is deformed due to a factor such asthermal expansion, an appropriate gap dimension can be easilymaintained. For example, when using an annular induction heating coilassociated with a circular treatment target portion to perform the heattreatment based on a single shot heating process, since the workpiece isdeformed due to thermal expansion, the induction heating coil must beset to be large in advance, and there occurs a problem of poor heatingefficiency, but an appropriate gap can be maintained by just adjustingthe arrangement with respect to the workpiece when the cover ratio issmall like this embodiment.

14th Embodiment

An induction heating apparatus 210 according to a 14th embodiment of thepresent invention will now be described with reference to FIG. 27 toFIG. 30. It is to be noted that structures are equal to those in the13th embodiment except that a treatment target portion N2 and a heatingconductor portion 331 are inclined with respect to an axis C1, therebyomitting a repeated explanation.

FIG. 27 is a perspective view showing configurations of a heatingconductor portion 331 of the induction heating apparatus 210 and aworkpiece W2 according to this embodiment, FIG. 28 is a plan view, FIG.29 is a side view, and FIG. 30 is an explanatory view showing a part ofthe configurations.

In this embodiment, the workpiece W2 has a solid frustum-like shape, andthe treatment target portion N2 which is a surface on one end side in anaxial direction is inclined with respect to the axial direction and aradial direction. That is, the treatment target portion N1 is a planarsurface orthogonal to the axis in the first embodiment, but thetreatment target portion N2 forms an inclined surface that is inclinedwith respect to the axis in this 14th embodiment.

A basic configuration of a heating conductor portion 331 is the same asthat of the heating conductor portion 231 according to the firstembodiment, and bent portions 334 and 335 and conductor portions 336that connect these bent portions are continuously configured. Each ofthe conductor portions 336 is extended to cross a circumferentialdirection R, configured in such a manner that a circumferential lengthof a part apart from an axis C1 which is the center of rotation islonger than a circumferential length of a part close to the axis C1, andformed in such a manner that a length in the circumferential directioncan be associated with a speed in the circumferential direction. Sincethe conductor portion 336 is bent in such a manner that an extensionangle of the part apart from the axis C1 with respect to thecircumferential direction R is smaller than an extension angle of thepart close to the axis C1 while maintaining a cross-sectional areaconstant, the speed and the length in the circumferential direction canbe associated with each other.

For example, here, as shown in FIG. 30, bending angles of α3=α4=150degrees, θ4=90 degrees, θ5=60 degrees, and θ6=30 degrees are set, and arelationship between a radius of rotation r1 of a reference point 34 onthe treatment target portion N1 facing a first part 336 a, a radius ofrotation r3 of a reference point P6 facing a third part 336 c, acircumferential dimension M4 of the first part 336 a, and acircumferential dimension M6 of the third part 336 c is set tor1:r3≈M4:M6. That is, the distance from the axis C1 and thecircumferential dimension are changed to be associated with each otherso that a movement speed and a dimension in a moving direction can beassociated with each other.

This embodiment can obtain the same effect as that in the 13thembodiment.

For example, as the example of effecting the relative movement, theexample of rotating the workpiece W1 to perform the relative movementhas been described in the foregoing embodiment, but the presentinvention is not restricted thereto, and the relative movement may beperformed by moving the heating conductor portion 231 side with apredetermined trajectory along the circumferential direction R.

15th Embodiment

Although the above has described the example where the heating conductorportion 231 or 331 is arranged at one position alone with respect to theone treatment target portion N1 or N2, the present invention is notrestricted thereto, and induction heating apparatuses 210 may bearranged along a circumferential direction R at equal intervals.

FIG. 31 shows a 15th embodiment of the present invention. That is, wheninstalling the two induction heating apparatuses 210, the two inductionheating apparatuses 210 are arranged at positions with central angles of180 degrees to face each other like the induction hardening apparatus202. Further, in the case of three induction heating apparatuses, theyare installed at positions with central angles of 120 degrees. When theplurality of induction heating apparatuses 210 are used, a cover ratioof one heating conductor portion can be reduced, and a treatment timecan be decreased to quickly terminate the heat treatment, and hence thisconfiguration is suitable when a workpiece has a large size inparticular.

Although each of treatment target portions N1 and N2 is exemplified by aplanar or inclined annular surface in the foregoing embodiments, thepresent invention is not restricted thereto, and the treatment targetportion can be applied to a circular shape or any other shape having aconcave portion or a step. Further, the solid frustum shape has beendescribed as an example in the 14th embodiment, but a hollow frustumshape may be adopted.

Although the flexure portion formed by bending the end of the bendingportion into a rectangular shape has been described as an example in theforegoing embodiment, the present invention is not restricted thereto,and it is possible to adopt a configuration having a curved portionhaving a shape curved into a semicircular shape.

Furthermore, although the example where the present invention is appliedto one end surface in the axial direction alone has been described, itcan be likewise applied to both end surfaces when forming each of bothend surfaces in the axial direction into a circular plane or an inclinedsurface.

16th Embodiment

Although the conductor portion is sectioned into three parts in theradial direction in the foregoing embodiments, the present invention isnot restricted thereto. It may be partitioned into two, four, or moreparts.

FIG. 32 shows a 16th embodiment according to the present invention. Forexample, like a conductor portion 346 shown in FIG. 32, four or moreparts 346 a, 346 b, 346 c, and 346 d may be set and finely separated toassociate a circumferential speed and a circumferential dimension witheach other.

17th Embodiment

FIG. 33 shows a 17th embodiment according to the present invention. Likea conductor portion 356 depicted in FIG. 33, the conductor portion maybe smoothly curved so that an angle gradually increases with decreasingdistance to the outer side in the radial direction, thereby associatinga circumferential speed and a circumferential dimension with each other.In each of the conductor portion 346 and the conductor portion 356, adimension orthogonal to an extending direction C3 or C4 indicated by adotted line in the drawing (dashed arrows) is fixed, and a dimension ina moving direction R (solid arrows) is changed to be associated with aspeed in the moving direction P while keeping a uniform cross-sectionalarea. Moreover, the sectionalization in the radial direction may beequal division.

Additionally, as the example in which the distance from the center ofrotation is associated with the circumferential dimension, theconfiguration in which the distance from the center of rotation isproportionate to the circumferential dimension has been described, butthe present invention is not restricted thereto, and the presentinvention can be applied even though precise proportionality is notachieved.

18th Embodiment

FIG. 34 is an explanatory view schematically showing an entireconfiguration of a heat treatment apparatus according to thisembodiment. FIG. 35 to FIG. 37 are respectively a plan view, a sideview, and a front view of the heat treatment apparatus.

As shown in FIG. 34, a heat treatment apparatus 410 comprises a movementsupport unit 411 that movably supports a workpiece E1 as a treatmentobject, an induction heating portion 412 that inductively heats atreatment target portion U1 of the workpiece E1 while relatively movingwith respect to the treatment target portion U1, and a cooling unit 413(cooling unit) for cooling the workpiece 31 after a heat treatment stepfor the treatment target portion U1.

As shown in FIG. 35 to FIG. 38, the induction heating portion 412comprises a high-frequency power supply 421 as power supplying unit,lead wires 422 and 423 connected to the high-frequency power supply 421,a spacer 428 including a pair of conductive plates 424 and 425 connectedto the lead wires 422 and 423, an induction heating coil 425 having bothends connected to the pair of conductive plates 424 and 425, and a core427 (shown in FIG. 35 and FIG. 38 alone) arranged on a back side of aheating conductor portion 431 of the induction heating coil 426.

The workpiece E1 as an example of the processing object shown in FIG. 34is a radially thick component (a radially thick portion) having athickness of 25 mm or above and, for example, there is used acylindrical member having an outside radius r1=250 mm, an inside radiusr2=200 mm, a all thickness dimension S1=50 mm, and an axial (firstdirection) length S1=100 mm with the center of axis C1 at the center.The heating conductor portion 431 is arranged to face a part of atreatment target unit U1 of the workpiece E1 while assuring apredetermined gap dimension N1.

In this embodiment, for example, description will be given as to a casein which a circular strip-like region at a central part in the axialdirection on an outer peripheral surface of the workpiece E1 isdetermined as a treatment target unit U1 and a heat treatment isperformed with respect to the whole circumference of this treatmenttarget portion U1 as the radially thick portion. In this embodiment, a Zdirection which is the axial direction of the workpiece E1 is the firstdirection, and a circumferential direction R parallel to the outerperipheral surface of the workpiece E1 with the center of axis C1 at thecenter is a second direction. Here, a radial dimension in thecircumferential direction R is a value obtained by adding the gapdimension K1 to the radial dimension r1 of the outer peripheral surfaceof the workplace, and r1+K1 is obtained.

The treatment target portion U1 has an endless loop-like shape that iscontinuous along the circumferential direction on the outer peripheralsurface of the workpiece E1. When the workplace E1 is rotated on thecenter of axis C1, the treatment target portion U1 and the heatingconductor portion 431 are relatively moved along the circumferentialdirection R by the movement support unit 411.

As shown in FIG. 35 to FIG. 37, the induction heating coil 426continuously and integrally comprises a zigzag heating conductor portion431 facing the treatment target portion U1 of the workplace E1, a firstconnection conductor portion 432 that is continuous with one end side431 a of the heating conductor portion 431, and a second connectionconductor portion 433 that is continuous with the other end side 431 bof the heating conductor portion 431.

As shown in FIG. 37, the heating conductor portion 431 is formed ofconductor members 431 w and has a zigzag shape such that U-like bentportions 434 and 435 are opened toward the center C2 in the Z directionand alternately continuously arranged along the circumferentialdirection R so that these bent portions face each other. The bentportion 434 has a U-like shape opened toward the lower side, and thebent portion 435 has a U-like shape opened toward the upper side.

A total dimension R2 of the heating conductor portion 431 in the seconddirection is not lower than 1/10 and not creator than 1/2 of a dimensionof a whole circumference in the second direction of the treatment targetportion U1 facing the heating conductor portion 431. A cover ratio whichis a ratio of the dimension of the heating conductor portion 431 in thesecond direction to the treatment target portion U1 is set to beapproximately 1/10 here.

It is to be noted that R5 which is an interval of conductor members 431w adjacent to each other is set to be one times or above and two timesor below a dimension of P4 which is a width of the conductor member 431w. This is because currents adjacent to each other have opposeddirections to offset magnetic fluxes when the interval between theconductor members 431 w adjacent to each other is equal to or less thanthe width dimension of the conductor member 431 w, or the interval istoo large to deteriorate heating efficiency when the interval is greaterthan two times. In this embodiment, the dimensions are set to R4=15 mmand R5=20 mm in FIG. 37.

The first connection conductor portion 432 continuously and integrallycomprises a conductor portion 432 a that extends from an end portion ofthe one end side 431 a of the heating conductor portion 431 in the Ydirection, a conductor portion 432 b that bends from an end portion ofthe conductor portion 432 a and extends toward the central side in theaxial direction of the conductive plate 424 along the X direction, aconductor portion 432 c that bends at the center of the conductive plate424 and extends in the Y direction, and a conductor portion 432 d thatbends and extends in the Z direction. A coupler 436 configured toconnect is component such as a hose for a coolant is provided at an endportion of the first connection conductor portion 432.

The second connection conductor portion 433 continuously and integrallycomprises a conductor portion 433 a that extends from an end portion ofthe other end side 431 b of the heating conductor portion 431 in the Ydirection, a conductor portion 433 b that bends from an end portion ofthe conductor portion 433 a and extends toward the central side in theaxial direction of the conductive plate 425 along the X direction, aconductor portion 433 c that bends at the center of the conductive plate425 and extends in the Y direction, and a conductor portion 433 d thatbends and extends in the Z direction. A coupler 437 configured toconnect a component such as a hose for a coolant is provided at an endportion of the second connection conductor portion 433.

The first connection conductor portion 432 and the second connectionconductor portion 433 are arranged apart from each other in a thickness(Z axis) direction to sandwich a space 428 therebetween. The spacer 428is constituted by overlapping the pair of conductive plates 424 and 425each having a rectangular tabular shape and a rectangular tabularinsulating plate 438 sandwiched between the pair of conductive plates424 and 425 and fixing the conductive plates 424 and 425 and theinsulating plate 428 through insulating bushes 439 by bolts 441 and nuts442. The respective conductive plates 424 and 425 are connected to thehigh-frequency power supply 421 through the lead wires 422 and 423.

As shown in a cross-sectional view of FIG. 38, the induction heatingcoil 426 is formed into, e.g., a rectangular hollow shape from amaterial such as copper. This hollow portion 426 a serves as a paththrough which the coolant circulates. The induction heating coil 426 isset to have a width dimension W1=15 mm and a thickness dimension T1 inthe Y direction=10 mm.

The core 427 is made of a material having high permeability such as asilicon steel sheet, a polyiron core, or FERROTRON and arranged on theback side of the heating conductor portion 431. The core 427 has athickness T2=approximately 5 mm and is formed into a shape having aU-like cross section that integrally includes both side portions of theheating conductor portion 431 and a rear wall portion.

The movement support unit 411 depicted in FIG. 34 rotates the workplaceE1 on the center of axis C1 in a state that the workpiece E1 is set at apredetermined position. At this time, the movement support unit 11performs control so that the cap dimension E1, between the heatingconductor portion 431 and the workpiece E1 can be maintained at apredetermined value. Further, after the end of the heat treatment overthe whole circumference (the whole stroke) of the treatment target unitU1, the movement support portion 411 moves the workpiece E1 to the lowercooling unit 413 along the axial direction.

The cooling unit 413 provided below the heating coil 426 is constitutedas a cylindrical shape to surround the outer side of the workpiece E1,which has been moved to the lower side after the heat treatment, andcools the workpiece E1 arranged in an inner space 413 a.

A heat treatment method according to this embodiment will now bedescribed. The heat treatment method according to this embodimentcomprises a moving and heating step of relatively moving the treatmenttarget portion U1 while heating the same and a cooling step of coolingthe treatment target portion U1 after she moving and heating step.

At the moving and heating step, when the high-frequency power supply 421is turned on in a state that the heating conductor portion 431 isarranged to face a part of the treatment target portion U1 as shown inFIG. 34 to FIG. 37, a high-frequency current flows through the lead wire422, the first conductive plate 424, the first connection conductorportion 432, the heating conductor portion 431, the second connectionconductor portion 433, the second conductive plate 425, and the leadwire 423 in the mentioned order and returns to the high-frequency powersupply 421.

At this time, in the heating conductor portion 431, the high-frequencycurrent flows from the one end 431 a side to the other end 431 b side asindicated by arrows in FIG. 35 to FIG. 37, and an induction current isgenerated on the surface of the heating conductor portion 431 to heatthe oppositely arranged treatment target portion U1.

At this time, when the workpiece E1 is rotated in a state that the gapdimension K1 between the surface of the treatment target portion U1 ofthe workpiece E1 and the surface of the heating conductor portion 431 ismaintained at the predetermined value, the heating conductor portion 431relatively moves with respect to the treatment target portion U1 in thesecond direction at a predetermined speed.

For example, here, the relative movement is performed at a speed of 200to 300 mm/sec while maintaining a power of 100 to 150 kW and the gapdimension K1=2.5 mm.

With the above-described operation, the entire region of the treatmenttarget portion U1, which is a strip-like region on the outer peripheralsurface of the workpiece E1 arranged to face the heating conductorportion 431, is uniformly heated.

After the end of the heat treatment over the whole circumference of thetreatment target portion U1, the movement support unit 411 moves theworkpiece 61 to the lower cooling unit 413 along the Z direction. Thecooling unit 413 uses a coolant to cool the workpiece E1 arranged in thespace 413 a which is a cooling region surrounded by a cooling jacket.

Moreover, when the coolant flows through the hollow portion 426 a in theinduction heating coil 426 and the hollow portion 426 a of the firstconnection conductor portion 432, the heating conductor portion 431 andthe second connection conductor portion 433, the induction heating coil426 and the conductive plates 124 and 425 are cooled.

According to the induction heating coil, the heat treatment apparatus,and the heat treatment method of this embodiment, the following effectcan be obtained. That is, since the heating conductor portion 131 isformed into a zigzag shape continuously having the flexure portions, aferromagnetic field can be assured, and an excellent temperature patterncan be obtained. Therefore, the high-speed and uniform heat treatmentcan be performed with low power.

For example, coil efficiency is approximately 30% when a hairpin-likecoil is used whereas the coil efficiency of approximately 70% can beassured when the zigzag shape as in this embodiment is used.

Moreover, when the interval between the conductor members 431 w adjacentto each other is set to be one times or above and two times or below thewidth dimension of the conductor member 431 w of the heating conductorportion 431, the offset of magnetic fluxes can be avoided, and theself-loss of the coil can be reduced.

When the zigzag heating conductor portion 431 according to thisembodiment is used, an end-point temperature of 850 degrees can berealized on the surface of the treatment target portion U1 with power of100 kW by setting a speed of 200 to 300 mm/sec and a heating time=300 s.That is when the induction heating coil 426 having the zigzag heatingconductor portion 431 is used, it is possible to realize the heattreatment for a large workpiece based on scanning partial heating thatcannot be realized by, e.g., a tabular induction heating coil.

Additionally, it is possible to perform the uniform heat treatment withno soft zone at a start end and a termination end of the treatment whenthe treatment target portion U1 has a loop-like shape even though thepartial heating is used.

Therefore, for example, when a roller bearing is a workpiece and araceway surface on which a rolling element passes is the treatmenttarget portion U1, a on hardened layer having no soft zone can beformed, and hence particularly excellent characteristics can beobtained.

Since the heat treatment is carried out while arranging the conductorportion to face a part of the treatment target portion U1 and performingthe relative movement, when the treatment target portion U1 and theworkpiece E1 are large, a size of the heating conductor portion 431 canbe reduced by arranging the plurality of heating conductor portions 431,thereby miniaturizing the heat treatment apparatus 410. Therefore, thenecessary power can be decreased, and a manufacturing cost can besuppressed.

Further, since the heat treatment is carried out while arranging theconductor portion to face a part of the treatment target portion U1 andperforming the relative movement, for example, when a circular memberhaving bent portions is a workpiece, an appropriate gap dimension can beeasily maintained even though the workpiece is deformed due to a factorsuch as thermal expansion at the time of induction heating. For example,when using an annular induction heating coil associated with a circulartreatment target portion to perform the heat treatment adopting a singleshot heating process, since the workpiece is deformed due to thermalexpansion, the induction heating coil must be set to have a larger sirein advance, heating efficiency is deteriorated, but an appropriate gapcan be maintained by just adjusting the arrangement with respect to theworkpiece when a cover ratio is small, as in this embodiment.

It is to be noted that a part in the workpiece having a thickness of 25mm or above is determined as a radially thick component (a radiallythick portion).

For example, although the description has been given as to the case thatthe relative movement is effected by rotating the workpiece E1 in theforegoing embodiment, the present invention is not restricted thereto,and the relative movement may be effected by moving the inductionheating portion 412 side with a predetermined trajectory parallel to shesecond direction. Although the two bent portions 434 and the two bentportions 435 are arranged, the present invention is not restricted, andthe number of the bent portions 434 or 435 may be one, three, or above,and the number of the bent portions 434 may be different from the numberof the bent portions 435.

Although the description has been given as to the example where the oneinduction heating portion 12 is arranged at one position with respect tothe one treatment target unit U1 in the foregoing embodiment, thepresent invention is not restricted thereto, and a plurality ofinduction heating portions 412 may be arranged along the seconddirection.

19th Embodiment

For example, in the case of installing two induction heating portions412, two induction heating coils 426 are arranged at positions havingcentral angles deviated by 180 degrees so that the coils face eachother, and each central angle is set to 120 degrees when three inductionheating coils are arranged.

20th Embodiment

Although the heating conductor portion 431 is configured to curve sothat its center protrudes beyond its both ends when seen in a plan viewin the foregoing embodiment, the present invention is not restrictedthereto, and the heating conductor portion 431 can be appropriatelychanged in accordance with a shape of a workplace. FIG. 40 shows a 20thembodiment according to the present invention. When an inner peripheralsurface of a circular workpiece E2 is a treatment target portion U2, theheating conductor portion 431 is configured to curve in a directionopposite to the above direction so that both end portions protrudebeyond a central side.

21st Embodiment

FIG. 41 shows a 21st embodiment according to the present invention. Whena flat surface of a workplace E3 is a treatment target portion U3, aheating conductor portion 431 is configured to have a linear shape asseen in a plan view. It is to be noted that the linear X direction is asecond direction. In such a case, the same effects as those of theforegoing embodiments can be likewise obtained.

22nd Embodiment

FIG. 42 shows a 22nd embodiment according to the present invention.Although the bent portion 434 or 435 bent into the U-like rectangularshape has been described as an example of the flexure portion in theforegoing embodiment, the present invention is not restricted thereto.For example, as shown in FIG. 42, curved portions 534 and 535 curvedinto a semicircular shape may be formed. In this case, heating iscarried out with a temperature pattern such that the heating isconcentrated on the center C2 in the first direction. Therefore, thisconfiguration is preferable when increasing a heating temperature on thecenter C2 side is desired.

Although the configuration in which the arc-like surface having auniform thickness is the treatment target portion U1 has been describedas the example in the foregoing embodiment, the present invention is notrestricted thereto, and the surface of the treatment target portion maybe inclined, or the treatment target portion may have a step portion,e.g., a concave portion.

Although the case that the work piece has the radius of approximately250 mm and the cover ratio of approximately 1/10 has been described inthe foregoing embodiment, the present invention is not restrictedthereto. For example, the range of the cover ratio can be appropriatelychanged in accordance with conditions such as a diameter of a workpiece,and the cover ratio of 1/10 or above and 1/2 or below and 1/10 to 1/3 ispreferable, for example. When the cover ratio is less than 1/10,sufficient heating cannot be performed. When the cover ratio exceeds1/2, enabling the coil to follow expansion of the workpiece at the timeor heating is difficult. Moreover, a facility cost is increased.

As another embodiment according to the present invention, for example,in regard to dimensions of the treatment target portion U1, when anoutside diameter r1 of a workpiece=ϕ1000 mm and a height S1=110 mm areset, the heating conductor portions 431 are installed at two positionsto face the treatment target portion U1, a total circumferentialdimension of the heating conductor portions 431 at the two positions isset to 600 mm, and a cover ratio is set to approximately 1/5. In thiscase, heat treatment conditions are a power of 140 kW and a heatingtime=310 s, and an end-point temperature on the surface of the treatmenttarget portion U1 is set to 900 degrees to realize the heat treatment.

Additionally, as still another embodiment according to the presentinvention, for example, in regard to dimensions of the treatment targetportion U1, when an outside diameter r1 of a workpiece=ϕ3000 mm and aheight S1=135 mm are set, the heating conductor portions 431 areinstalled at four positions to face the treatment target portion U1, atotal circumferential dimension of the heating conductor portions 431 atthe four positions is set to 2400 mm, and a cover ratio is set toapproximately 1/4. In this case, heat treatment conditions are a powerof 185 kW and a heating time=280 s, and an end-point temperature on thesurface of the treatment target portion U1 is set to 920 degrees torealize the heat treatment.

23rd Embodiment

FIG. 43 is a plan view in which four induction heating coils 426 arearranged while shifting a central angle every 90 degrees as a 23rdembodiment according to the present invention. A cover ratio is set to1/3 and four heating conductor portions 431 are arranged along a seconddirection. Here, a total cover ratio of the four heating conductorportions 431 arranged at equal intervals is set to 1/3. When the coverratio is set in this manner, an induction heating apparatus can beminimized while maintaining a desired treatment time and treatmentefficiency. Furthermore, when more than one induction heating portion410 is used, the treatment time can be reduced, and the heatingtreatment can be rapidly completed, which is preferable when a size of aworkpiece is large.

It is to be noted that the present invention is not restricted to theforegoing embodiments. For example, treatment conditions, or specificshapes, materials, dimensions, and other aspects of respectiveconstituent elements such as a workpiece or a coil are not restricted tothe examples described in the foregoing embodiments, and they can beappropriately changed. Moreover, some constituent elements may beeliminated from all the constituent elements described in theembodiments. Additionally, constituent elements in different embodimentsmay be combined. Further, it is needless to say that variousmodifications can be made without departing from the gist of the presentinvention.

According to the present invention, it is possible to provide thetechnology that can readily realize a heat treatment for a desiredheated region, the technology that enables a uniform treatment, and thetechnology that can improve heat treatment efficiency even when a largetreatment object is to be inductively heated.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:
 1. A method of inductivelyheat treating a treatment object, comprising: arranging a second heatingconductor portion of a second heating coil at a second distance from arotational axis to face a convex treatment region of the treatmentobject, the convex treatment region having an outermost surface with asecond radius relative to the rotational axis, the second distance beinggreater than the second radius; arranging a first heating conductorportion of a first heating coil at a first distance from the rotationalaxis that is smaller than the second radius, to face a concave treatmentregion of the treatment object having a different position along therotational axis than the convex treatment region and having an outermostsurface with a first radius that is smaller than the second radius; andmoving the treatment object relative to the first and second heatingconductor portions along a circumferential direction of the treatmentobject while inductively heating the convex treatment region using thesecond heating conductor portion and inductively heating the concavetreatment region using the first heating conductor portion, such thatthe convex treatment region and the concave treatment region form onecontinuous heating treatment region.
 2. The method according to claim 1,further comprising moving the treatment object to a lower cooling unitafter moving the treatment object relative to the first and secondheating conductor portions along the circumferential direction by anentire stroke of the convex treatment region and the concave treatmentregion.
 3. The method of claim 1, wherein at least one of the first orsecond heating coils have a zigzag shape in which a first bent portionwith a first leg and a second leg opens toward a first side of therotational axis, and a second bent portion with a third leg and a fourthleg opens toward a second side of the rotational axis, with the firstleg, the second leg, the third leg, and the fourth leg being spaced awayfrom the rotational axis by a common distance.
 4. The method of claim 3,wherein the first heating conductor portion has the zigzag shape, andthe second heating conductor portion has a hairpin shape.
 5. The methodof claim 1, wherein moving the treatment object relative to the firstand second heating conductor portions comprises maintaining a secondpredetermined gap between the first heating conductor portion and anouter surface of the convex treatment region, and maintaining a firstpredetermined gap between the first heating conductor portion and anouter surface of the concave treatment region, to control for thermalexpansion of the treatment object.
 6. The method of claim 1, wherein thefirst heating conductor portion is one of a plurality of alike heatingconductors of a plurality of alike heating coils, wherein arranging thefirst heating conductor portion of the first heating coil at the firstdistance from the rotational axis to face the concave treatment regionof the treatment object comprises arranging the plurality of alikeheating conductors at the first distance from the rotational axis toface the concave treatment region at different positions about therotational axis, wherein the plurality of alike heating conductors coverbetween about 1/10 and about 1/2 of the outermost surface of the concavetreatment region.
 7. The method of claim 1, wherein a cover ratio of thesecond heating conductor portion relative to the outermost surface ofthe convex treatment region differs from a cover ratio of the firstheating conductor portion relative to the outermost surface of theconcave treatment region.
 8. The method of claim 1, wherein at least oneof the first heating conductor portion or the second heating conductorportion has an arc-like shape.
 9. The method of claim 1, wherein atleast one of the outermost surface of the convex treatment region or theoutermost surface of the concave treatment region are inclined withrespect to the rotational axis.
 10. The method of claim 1, wherein theoutermost surface of the convex treatment region and the outermostsurface of the concave treatment region form a stepped outer treatmentsurface of the treatment object in an axial direction.